Lecture 4 - Anaphylaxis Flashcards
What is the definition of anaphylaxis?
- A serious, life-threatening generalized or systemic hypersensitivity reactions
- A serious allergic reaction that is rapid in onset and might cause death
What is the pathophysiology of anaphylaxis?
- An acute systemic, allergic reaction
- During an initial exposure, individual will form IgE antibodies
- Subsequently, when the individual is exposed to the antigen, it will bind to IgE antibodies => release of vasoactive and inflammatory mediators from mast cells and basophils
- May cause urticaria, angioedema, bronchospasm, hypotension, and GI symptoms
How long do it generally take for anaphylaxis signs and symptoms to occur after exposure?
30 minutes, but can be several hours
What are the 3 categories of anaphylaxis?
1) Immunologic (IgE-mediated or non-IgE-mediated)
2) Nonimmunologic
3) Idiopathic
What is the clinical criteria for anaphylaxis?
- Any one of the three
1) Acute onset of an illness (minutes to hours) w/ the involvement of the skin, mucosal tissue, or both AND respiratory compromise and/or reduced BP or associated symptoms of end-organ dysfunction
2) 2 or more of the following occur rapidly after exposure to a likely allergen - involvement of skin/mucosal tissue, respiratory compromise, reduced BP, persistent GI symptoms
3) Reduced BP after exposure to known allergen
What are the 3 different potential patterns of anaphylactic reactions?
1) Uniphasic
2) Biphasic
3) Protracted
What is a uniphasic anaphylactic reaction?
- Isolated reaction w/ signs and symptoms usually appearing w/in 30 minutes of exposure to allergen
- Spontaneously settles or resolves w/ treatment, generally w/in 1-2 hours
What is a biphasic anaphylactic reaction?
- Anaphylaxis reaction resolves, then symptoms begin again usually w/in 8 hours of first symptoms
- Occurs in up to 20% of patients experiencing anaphylaxis
What is a protracted anaphylactic reaction?
Severe reaction that lasts for an extended time (24-32 hours)
What are the signs and symptoms of anaphylaxis?
- Cutaneous - hives, severe itching, flushing/redness of skin, swelling
- Respiratory - throat or chest tightness, difficulty breathing, wheeze, cough, swelling of tongue, itching of throat
- GI - difficulty or pain swallowing, nausea or vomiting, diarrhea
- CV - hypotension, chest pain, dysrhythmias
- Other reactions - lightheadedness, dizziness, sweating, sudden behavioural changes
What are common triggers of anaphylaxis?
- Foods - peanuts, tree nut, shellfish, milk, eggs
- Drugs - antibiotics, NSAIDs, biologics
- Insect stings - honeybees, yellow jackets, hornets, wasps, fire ants
- Latex
What is the initial treatment for anaphylaxis in the community setting?
- CPR if breathing is affected
- Epinephrine injected immediately; repeat in 10 minutes if needed
- Call 911
What is the mechanism of action for epinephrine autoinjectors?
Act on alpha and beta-adrenergic receptors, leading to restoration of respiratory and CV function by relaxation of bronchial smooth muscle and vasoconstriction to reverse hypotension and stimulate the heart
What is the recommended administration of epinephrine autoinjectors?
Intramuscularly in the mid to outer thigh
What are the various delivery systems for an epinephrine autoinjector?
- EpiPen
- Allerject (not currently available and unknown if it will become available)
- Twinject (discontinued)
- Generics
Epinephrine autoinjectors are a schedule __ medication
2
What is the adult dose of EpiPen?
0.3 mg/dose